Currently running SmartTrack v12 with queues using Office 365 mailboxes for its pop/smtp.
Also using Office 365 for our Outlook email.
Now, since a couple of days ago, anything sent from SmarterTrack to some customers gets delivered (checked via Exchange online logs) but doesn't hit the end mailbox.
If I email the same email from Outlook it gets delivered and hits the end mailbox.
Same domain, DKIM/SPF etc, just what is being used is different. I have tested using a SmarterTrack queue that isn't a commonly used one (i.e. sales@) so it wouldn't have an block on it at customer end.
I can see at some customers email servers that they have email security devices, and I'm thinking this is what is preventing the emails getting through.
Otherwise, if I email to my gmail account via ST or Outlook it does arrive, and shows all Passes on DKIM/SPF etc.
Also trying to get some assistance from the admins at our customers end but that is slow going so trying to see if anyone has any ideas or suggestions from ST end.